The term “thermoelectricity” means the mutual influence of temperature and electricity and their conversion into each other. Thermoelectric materials make use of this influence in order to generate electrical energy from waste heat as thermoelectric generators, but are also used in the form of what are known as heat pumps, if electrical energy is used to transport heat from a temperature reservoir having a lower temperature to one having a higher temperature.
Precisely the latter thermoelectric heat pumps are used in vehicle technology to cool a wide variety of components such as modern lithium ion batteries, which emit waste heat in considerable amounts during operation. Such thermoelectric heat pumps can however also be used in electric vehicle as combined heating and cooling devices, for instance for the temperature control of the passenger compartment, especially as they have a much higher efficiency than for instance conventional electric resistance heaters. In motor vehicles having an internal combustion engine, thermoelectric generators can convert some of the waste heat generated in the exhaust gas during the combustion process and feed it into the on-board power supply of the motor vehicle. The waste heat that has been converted into electrical energy can thus be made useful in order to reduce the energy consumption of the motor vehicle to a functionally necessary minimum and consequently avoid unnecessary emission of exhaust gases such as CO2.
The fields of use of thermoelectric devices in automotive engineering are therefore many and varied. In each of the said use scenarios, it is of critical importance that the highest possible degree of efficiency is achieved in order to convert heat into electrical energy or vice versa as effectively as possible. The use in motor vehicles furthermore results in the additional requirement of producing thermoelectric devices in compact form. Thermoelectric devices installed in vehicles are therefore often produced in a plate or layer design, the thermoelectrically active elements being arranged inside a thermally conductive housing. The housing can thus be connected thermally to a temperature reservoir of low temperature on one side, the “cold” side, and to a temperature reservoir of higher temperature on the other side, the hot side, so that the thermoelectric elements produce an electric thermovoltage owing to the temperature gradient between the two sides, which thermovoltage can be conducted out via suitable electrical connections and used. In this case the thermoelectric device follows the working principle of a thermoelectric generator. Conversely, a thermoelectric device can also be used as a heat pump for transporting heat from the cold side to the hot side by applying an external electric voltage to the said electrical connections.
Against this background, WO 2012/12006 A2 concerns a thermoelectric module having a fluid-tight, metallic housing to which a ceramic layer is applied. At least one thermoelectrically active material is arranged in the housing.